Member of the Wildlife & Environment
Society of South Africa Western Cape Region

Eco Bites

Midges or Muggies

It is that time of the year
again – with the warmer weather
the little flying terrors are
out in force.

Midges, 'muggies', gnats – call
them what you like, they are a
nuisance and many residents in are being severely
pestered by these little guys.

What are they, and where do they
come from?

Midges, gnats or muggies is a
name applied to a wide range of
small flies. These are members
of the order Diptera (meaning
two-winged: di = two, ptera =
wings), this is the order to
which all flies belong. Midges
are not a well-defined group,
but are spread throughout at
least ten families in the
suborder Nematocera. This means
that their life-styles and
biology differ considerably;
some feed on nectar or
decomposing plant material, a
few feed on blood, and in some
species the adults do not feed
at all.

Like
all Diptera they have four life
stages: egg, larva, pupa and
adult. The larval stage in most
midges, with the exception of
the gall midges, are aquatic.
This means that the eggs are
laid in or near water or very
moist areas, the larvae are
found in the water, in mud in
the bottom of rivers, lakes or
ponds, or even in very wet leaf
mould in forests and other damp
places. Some larvae will inhabit
wet animal dung. The larval
stage for midges vary from only
a few days long, to several
years in cold climates; they
larvae feed on detritus, diatoms
and other microscopic plants and
animals.

The larvae turn into pupae, this
is mostly a fairly short stage,
mostly only two to four days,
although there are exceptions
where the pupal stage is longer.
The pupae do not feed at all.

The
adults will hatch from the
pupae, and these are the little
fellows that are such a nuisance
to us. Most species are
completely harmless, but there
are some that can cause
problems. The gall midges in the
family Cecidomyiidae are
important plant pests which can
affect crops. The biting midges
in the family Ceratopogonidae
are serious pests and are
responsible for spreading
livestock diseases like Blue
Tongue in cattle and sheep and
African Horse Sickness.

The female biting midges must
have a blood meal for their eggs
to mature, while feeding they
transmit parasites – most of
these parasites affect livestock
and game, but the midges can
infect humans with filarial
worms of the genus Mansonella.
This infection is not serious as
the worms are only located in
the skin, but it does cause
dermatitis and skin lesions.

The most common midge or muggie
that pesters us here in our area
are non-biting midges of the
family Chironomidae. There are
over 5,000 species occurring all
over the world, from the Arctic
regions in the north to the
Antarctic in the south, the
adults are small and resemble
mosquitoes – but most of them do
not feed at all.

A
distinguishing characteristic of
several chironomid species is
that the larvae have haemoglobin
in their blood, this means that
their blood is red – these are
often known as bloodworms. They
can store oxygen in their blood
which allows them to survive in
deep water or in water where the
oxygen content is low. Many of
the local species of chironomid
have bloodworm larvae, you can
find these larvae quite commonly
in ponds and small water bodies
in the area.

While
adult chironomids are harmless,
they can be pests when they
emerge in large numbers. They
can damage paint, brick and
other surfaces with their
droppings, and when they die
they build up in piles.
Sometimes these piles of dead
muggies provoke allergic
reactions in sensitive
individuals. In most areas
chironomids breed once or twice
a year, but if conditions are
good they can breed up to four
times. Each breeding cycle
delivers a swarm, so we can have
swarms up to four times a year;
another factor is that breeding
in different water areas are
staggered, so one could be
suffering a series of swarms
from different water bodies, or
even from the same water, for a
few months at a time.

While they are a nuisance to us,
chironomid larvae and pupae are
important as food for fish,
amphibians and other aquatic
organisms; the adults are a very
popular food source for
insectivorous birds such as
swallows and martins. Chironomid
larvae are also useful as an
indicator of water quality – the
presence or absence of various
species is an indication of the
quality of the water. Some like
the bloodworms become more
numerous in polluted waters
where oxygen levels are very
low, other members of the family
are intolerant of poor water
quality and will only be found
where the water quality is good.

How do you deal with these
pests?

In the daytime they are a
nuisance if you happen to walk
into a swarm; the real problem
is at night as they are
attracted to lights. If they
really are a continuous
nuisance, the only way to keep
them out of your house is to put
up mosquito netting. There are
insect repellents on the market
today that will help, most of
these insecticides are specific
to insects and will not affect
humans or pets in the house; the
evaporative repellents (those
that are plugged into a wall
plug) for mosquitoes are quite
effective to keep a room clear
of midges.

And what about mosquitoes?

Midges are sometimes confused
with mosquitoes, but mosquitoes
are in the family Culicidae –
read more about them ....
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